diff --git a/gnu/local.mk b/gnu/local.mk
index fd3cc88af5..0b4a6c789f 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1226,6 +1226,8 @@ dist_patch_DATA =						\
   %D%/packages/patches/lirc-localstatedir.patch			\
   %D%/packages/patches/lirc-reproducible-build.patch		\
   %D%/packages/patches/llvm-3.5-fix-clang-build-with-gcc5.patch	\
+  %D%/packages/patches/llvm-9-fix-lpad-miscompilation.patch	\
+  %D%/packages/patches/llvm-9-fix-scev-miscompilation.patch	\
   %D%/packages/patches/lm-sensors-hwmon-attrs.patch		\
   %D%/packages/patches/lrcalc-includes.patch    		\
   %D%/packages/patches/lrzip-CVE-2017-8842.patch		\
diff --git a/gnu/packages/llvm.scm b/gnu/packages/llvm.scm
index 11e4cfbe4c..7723ff5bc1 100644
--- a/gnu/packages/llvm.scm
+++ b/gnu/packages/llvm.scm
@@ -15,6 +15,7 @@
 ;;; Copyright © 2019 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2019 Brett Gilio <brettg@gnu.org>
 ;;; Copyright © 2020 Giacomo Leidi <goodoldpaul@autistici.org>
+;;; Copyright © 2020 Jakub Kądziołka <kuba@kadziolka.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -510,7 +511,11 @@ output), and Binutils.")
        (uri (llvm-download-uri "llvm" version))
        (sha256
         (base32
-         "16hwp3qa54c3a3v7h8nlw0fh5criqh0hlr1skybyk0cz70gyx880"))))))
+         "16hwp3qa54c3a3v7h8nlw0fh5criqh0hlr1skybyk0cz70gyx880"))
+       (patch-flags '("-p2"))
+       (patches (search-patches
+                  "llvm-9-fix-scev-miscompilation.patch"
+                  "llvm-9-fix-lpad-miscompilation.patch"))))))
 
 (define-public clang-runtime-9
   (clang-runtime-from-llvm
diff --git a/gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch b/gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch
new file mode 100644
index 0000000000..6cfe07e50a
--- /dev/null
+++ b/gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch
@@ -0,0 +1,97 @@
+From 011fb5bf8b31316472fccb1a19c91912246df9b2 Mon Sep 17 00:00:00 2001
+From: Reid Kleckner <rnk@google.com>
+Date: Sat, 28 Mar 2020 11:03:14 -0700
+Subject: [PATCH] [CodeGen] Fix sinking local values in lpads with phis
+
+There was already a test case for landingpads to handle this case, but I
+had forgotten to consider PHI instructions preceding the EH_LABEL in the
+landingpad.
+
+PR45261
+---
+ llvm/lib/CodeGen/SelectionDAG/FastISel.cpp | 17 +++++++++-
+ llvm/test/CodeGen/X86/sink-local-value.ll  | 36 ++++++++++++++++++++++
+ 2 files changed, 52 insertions(+), 1 deletion(-)
+
+diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+index 5ac3606dc662..2638b1e8a05c 100644
+--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
++++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+@@ -225,6 +225,21 @@ static bool isRegUsedByPhiNodes(unsigned DefReg,
+   return false;
+ }
+ 
++static bool isTerminatingEHLabel(MachineBasicBlock *MBB, MachineInstr &MI) {
++  // Ignore non-EH labels.
++  if (!MI.isEHLabel())
++    return false;
++
++  // Any EH label outside a landing pad must be for an invoke. Consider it a
++  // terminator.
++  if (!MBB->isEHPad())
++    return true;
++
++  // If this is a landingpad, the first non-phi instruction will be an EH_LABEL.
++  // Don't consider that label to be a terminator.
++  return MI.getIterator() != MBB->getFirstNonPHI();
++}
++
+ /// Build a map of instruction orders. Return the first terminator and its
+ /// order. Consider EH_LABEL instructions to be terminators as well, since local
+ /// values for phis after invokes must be materialized before the call.
+@@ -233,7 +248,7 @@ void FastISel::InstOrderMap::initialize(
+   unsigned Order = 0;
+   for (MachineInstr &I : *MBB) {
+     if (!FirstTerminator &&
+-        (I.isTerminator() || (I.isEHLabel() && &I != &MBB->front()))) {
++        (I.isTerminator() || isTerminatingEHLabel(MBB, I))) {
+       FirstTerminator = &I;
+       FirstTerminatorOrder = Order;
+     }
+diff --git a/llvm/test/CodeGen/X86/sink-local-value.ll b/llvm/test/CodeGen/X86/sink-local-value.ll
+index b0e511ac1189..f7d861ac9b6c 100644
+--- a/llvm/test/CodeGen/X86/sink-local-value.ll
++++ b/llvm/test/CodeGen/X86/sink-local-value.ll
+@@ -145,6 +145,42 @@ try.cont:                                         ; preds = %entry, %lpad
+ ; CHECK:         retl
+ 
+ 
++define i32 @lpad_phi() personality i32 (...)* @__gxx_personality_v0 {
++entry:
++  store i32 42, i32* @sink_across
++  invoke void @may_throw()
++          to label %try.cont unwind label %lpad
++
++lpad:                                             ; preds = %entry
++  %p = phi i32 [ 11, %entry ]  ; Trivial, but -O0 keeps it
++  %0 = landingpad { i8*, i32 }
++          catch i8* null
++  store i32 %p, i32* @sink_across
++  br label %try.cont
++
++try.cont:                                         ; preds = %entry, %lpad
++  %r.0 = phi i32 [ 13, %entry ], [ 55, %lpad ]
++  ret i32 %r.0
++}
++
++; The constant materialization should be *after* the stores to sink_across, but
++; before any EH_LABEL.
++
++; CHECK-LABEL: lpad_phi:
++; CHECK:         movl    $42, sink_across
++; CHECK:         movl    $13, %{{[a-z]*}}
++; CHECK: .Ltmp{{.*}}:
++; CHECK:         calll   may_throw
++; CHECK: .Ltmp{{.*}}:
++; CHECK:         jmp     .LBB{{.*}}
++; CHECK: .LBB{{.*}}:                                # %lpad
++; CHECK-NEXT: .Ltmp{{.*}}:
++; CHECK:         movl    {{.*}}, sink_across
++; CHECK:         movl    $55, %{{[a-z]*}}
++; CHECK: .LBB{{.*}}:                                # %try.cont
++; CHECK:         retl
++
++
+ ; Function Attrs: nounwind readnone speculatable
+ declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+ 
diff --git a/gnu/packages/patches/llvm-9-fix-scev-miscompilation.patch b/gnu/packages/patches/llvm-9-fix-scev-miscompilation.patch
new file mode 100644
index 0000000000..3f16de5a2b
--- /dev/null
+++ b/gnu/packages/patches/llvm-9-fix-scev-miscompilation.patch
@@ -0,0 +1,113 @@
+Guix note: this got detected with the test suite of rustc 1.41.1, but
+the issue potentially affects all consumers of LLVM.
+
+From 58e8c793d0e43150a6452e971a32d7407a8a7401 Mon Sep 17 00:00:00 2001
+From: Tim Northover <tnorthover@apple.com>
+Date: Mon, 30 Sep 2019 07:46:52 +0000
+Subject: [PATCH] Revert "[SCEV] add no wrap flag for SCEVAddExpr."
+
+This reverts r366419 because the analysis performed is within the context of
+the loop and it's only valid to add wrapping flags to "global" expressions if
+they're always correct.
+
+llvm-svn: 373184
+---
+ llvm/lib/Analysis/ScalarEvolution.cpp              | 2 +-
+ llvm/test/Analysis/ScalarEvolution/limit-depth.ll  | 2 +-
+ llvm/test/Analysis/ScalarEvolution/nsw.ll          | 2 +-
+ llvm/test/Analysis/ScalarEvolution/trip-count12.ll | 2 +-
+ llvm/test/Analysis/ScalarEvolution/trip-count9.ll  | 8 ++++----
+ 5 files changed, 8 insertions(+), 8 deletions(-)
+
+diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
+index 354ae05bb841..c29fc5dbccfb 100644
+--- a/llvm/lib/Analysis/ScalarEvolution.cpp
++++ b/llvm/lib/Analysis/ScalarEvolution.cpp
+@@ -4992,7 +4992,7 @@ const SCEV *ScalarEvolution::createSimpleAffineAddRec(PHINode *PN,
+   // overflow.
+   if (auto *BEInst = dyn_cast<Instruction>(BEValueV))
+     if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L))
+-      (void)getAddRecExpr(getAddExpr(StartVal, Accum, Flags), Accum, L, Flags);
++      (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
+ 
+   return PHISCEV;
+ }
+diff --git a/llvm/test/Analysis/ScalarEvolution/limit-depth.ll b/llvm/test/Analysis/ScalarEvolution/limit-depth.ll
+index db68a4f84c91..6fdf8c5df974 100644
+--- a/llvm/test/Analysis/ScalarEvolution/limit-depth.ll
++++ b/llvm/test/Analysis/ScalarEvolution/limit-depth.ll
+@@ -46,7 +46,7 @@ define void @test_mul(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f) {
+ define void @test_sext(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f) {
+ ; CHECK-LABEL: @test_sext
+ ; CHECK:        %se2 = sext i64 %iv2.inc to i128
+-; CHECK-NEXT:   -->  {(1 + (sext i64 {(sext i32 (1 + %a)<nsw> to i64),+,1}<nsw><%loop> to i128))<nsw>,+,1}<nsw><%loop2>
++; CHECK-NEXT:   -->  {(1 + (sext i64 {(sext i32 (1 + %a) to i64),+,1}<nsw><%loop> to i128))<nsw>,+,1}<nsw><%loop2>
+ entry:
+   br label %loop
+ 
+diff --git a/llvm/test/Analysis/ScalarEvolution/nsw.ll b/llvm/test/Analysis/ScalarEvolution/nsw.ll
+index 69427368625d..ca24f9d4a04b 100644
+--- a/llvm/test/Analysis/ScalarEvolution/nsw.ll
++++ b/llvm/test/Analysis/ScalarEvolution/nsw.ll
+@@ -163,7 +163,7 @@ bb5:                                              ; preds = %bb2
+ declare void @f(i32)
+ 
+ ; CHECK-LABEL: nswnowrap
+-; CHECK: --> {(1 + %v)<nsw>,+,1}<nsw><%for.body>{{ U: [^ ]+ S: [^ ]+}}{{ *}}Exits: (2 + %v)
++; CHECK: --> {(1 + %v)<nsw>,+,1}<nsw><%for.body>{{ U: [^ ]+ S: [^ ]+}}{{ *}}Exits: (1 + ((1 + %v)<nsw> smax %v))
+ define void @nswnowrap(i32 %v, i32* %buf) {
+ entry:
+   %add = add nsw i32 %v, 1
+diff --git a/llvm/test/Analysis/ScalarEvolution/trip-count12.ll b/llvm/test/Analysis/ScalarEvolution/trip-count12.ll
+index 5e7d72d5e4f3..d0086ee2e6ac 100644
+--- a/llvm/test/Analysis/ScalarEvolution/trip-count12.ll
++++ b/llvm/test/Analysis/ScalarEvolution/trip-count12.ll
+@@ -1,7 +1,7 @@
+ ; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
+ 
+ ; CHECK: Determining loop execution counts for: @test
+-; CHECK: Loop %for.body: backedge-taken count is ((-2 + %len)<nsw> /u 2)
++; CHECK: Loop %for.body: backedge-taken count is ((-2 + %len) /u 2)
+ ; CHECK: Loop %for.body: max backedge-taken count is 1073741823
+ 
+ define zeroext i16 @test(i16* nocapture %p, i32 %len) nounwind readonly {
+diff --git a/llvm/test/Analysis/ScalarEvolution/trip-count9.ll b/llvm/test/Analysis/ScalarEvolution/trip-count9.ll
+index c0a1d12fa00e..9a080b34743f 100644
+--- a/llvm/test/Analysis/ScalarEvolution/trip-count9.ll
++++ b/llvm/test/Analysis/ScalarEvolution/trip-count9.ll
+@@ -179,7 +179,7 @@ exit:
+ }
+ 
+ ; CHECK: Determining loop execution counts for: @nsw_startx
+-; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x)<nsw> smax %n))
++; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax %n))
+ ; CHECK: Loop %loop: max backedge-taken count is -1
+ define void @nsw_startx(i4 %n, i4 %x) {
+ entry:
+@@ -195,7 +195,7 @@ exit:
+ }
+ 
+ ; CHECK: Determining loop execution counts for: @nsw_startx_step2
+-; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x)<nsw> smax %n)) /u 2)
++; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax %n)) /u 2)
+ ; CHECK: Loop %loop: max backedge-taken count is 7
+ define void @nsw_startx_step2(i4 %n, i4 %x) {
+ entry:
+@@ -381,7 +381,7 @@ exit:
+ }
+ 
+ ; CHECK: Determining loop execution counts for: @even_nsw_startx
+-; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x)<nsw> smax (2 * %n)))
++; CHECK: Loop %loop: backedge-taken count is (-1 + (-1 * %x) + ((1 + %x) smax (2 * %n)))
+ ; CHECK: Loop %loop: max backedge-taken count is -2
+ define void @even_nsw_startx(i4 %n, i4 %x) {
+ entry:
+@@ -398,7 +398,7 @@ exit:
+ }
+ 
+ ; CHECK: Determining loop execution counts for: @even_nsw_startx_step2
+-; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x)<nsw> smax (2 * %n))) /u 2)
++; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax (2 * %n))) /u 2)
+ ; CHECK: Loop %loop: max backedge-taken count is 7
+ define void @even_nsw_startx_step2(i4 %n, i4 %x) {
+ entry:
